Microfluidic devices have been used to explore a variety of biological problems of interest, ranging from fundamental research in protein crystallization to diagnostic assays. A number of these applications require the integration of valves, mixers, and other components into the devices in order to successfully carry out various steps. The incorporation of actively controlled functionalities, either directly in the device or via fixed interface with external components, often leads to more complex fabrication and the need for ancillary equipment. The use of passive and autonomous microfluidic components, while sometimes requiring more complex fabrication, can help to reduce or eliminate the need for additional equipment. Eliminating external components makes point-of-care devices more portable and facilitates operation of many devices in parallel, which is of particular interest for large parametric screening applications.
Many of the fabrication methods used to create microfluidic devices were first developed for microelectronics, so it is fitting that a number of parallels can be drawn between the two fields. Resistance, driving forces (pressure/voltage), and current (fluid/electrons) analogies are commonly used to compare electronic components and fluid networks. The analogy has been further extended in microfluidics to include diodes, rectifiers, memory elements, and capacitors. Two-phase flow has recently been used to encode and decode data sets using droplets. As with electronics, microfluidic components can be combined to form more complex devices and a microfluidic breadboard has already been demonstrated. Microfluidics can also be used to address problems that are not easily solved using standard computational methods. Regulatory systems can also be implemented in microfluidic devices. Responsive hydrogels have been used in microfluidic devices to regulate the pH or temperature of a solution. The use of pneumatic control in three dimensional channel structures has been shown as a means of self-regulation flow. Hence, it is highly desirable to couple a conditional action to more than one input, thereby enabling the creation of logic gates, which can be combined to perform computation and more complex functions.
Fluidic logic elements can be traced back to the 1950's; however, most of the early constructs depended on turbulent and multistable flow states, which are not scalable due to the low Reynolds numbers that are typically observed in microfluidic channels. More recent efforts using microfluidics have employed fluidic resistance, electrochemistry, pneumatics, channel geometry, multiphase flow, and chemistry to create logic elements. Many of these approaches rely on continuous flow and are unable to create more integrated constructs due to different input/output (e.g. pressure/dye). Additionally, the electronic components used to input and read out signals are more complex than the devices themselves. Ideally, fluidic logic elements would use consistent signal input/output and require minimal supporting equipment.
Therefore, it is a primary object and feature of the present invention to provide a method for controlling communication between multiple access ports in a microfluidic system in order to create a plurality of digital microfluidic circuit components.
It is a further object and feature of the present invention to provide a method for controlling communication between multiple access ports in a microfluidic system to create fluidic logic gates in the microfluidic system.
It is a still further object and feature of the present invention to provide a method for controlling communication between multiple access ports in a microfluidic system in order to allow various computations and complex functions to be performed with the system.
In accordance with the present invention, a method is provided of controlling communication between multiple ports in a microfluidic device. The method includes the step of providing a channel network in a microfluidic device. The channel network includes a first channel having a first input port and an output port. The first channel is filled with a fluid and a first output droplet is deposited on the output port. The first output droplet has a radius of curvature. The first output droplet flows toward the first input port in response to placement of a first input droplet having a radius of curvature greater than the radius of curvature of the first output droplet on the first input port.
The first channel includes a second input port. The first output droplet flows toward the second input port in response to placement of a second input droplet having a radius of curvature greater than the radius of curvature of the first output droplet on the second input port. The method also includes the additional step of depositing a first input droplet on the first input port. The first input droplet flows toward the output port in response to the first input droplet having a radius of curvature less than the radius of curvature of the first output droplet. A second input port is provided for the first channel. A second input droplet is deposited on the second input port. The second input droplet flows toward the output port in response to the second input droplet having a radius of curvature less than the radius of curvature of the first output droplet.
The channel network may include a second channel. The second channel has an input port and an output port. The input port of the second channel is placed in proximity to the output port of the first channel. The first output droplet communicates with the input port of the second channel when the first output droplet exceeds a predetermined volume. A second output droplet is deposited on the output port of the second channel. The second output droplet has a radius of curvature wherein the first output droplet flows toward the output port of the second channel in response to the first output droplet communicating with the input port of the second channel and having a radius of curvature less than the radius of curvature of the second output droplet on the output port of the second channel.
In accordance with a further aspect of the present invention, a method is provided of controlling communication between multiple ports in a microfluidic device. The method includes the step of providing a channel network in a microfluidic device. The channel network includes a first channel having first and second input ports and an output port. The first channel is filled with a fluid. A first output droplet is deposited on the output port. The first output droplet has a radius of curvature. A first input droplet is deposited on the first input port. The first input droplet flows toward the output port in response to the first input droplet having a radius of curvature less than the radius of curvature of the first output droplet. The first output droplet flows toward the first input port when the first input droplet has a radius of curvature greater than the radius of curvature of the first output droplet.
A second input droplet may be deposited on the second input port. The second input droplet flows toward the output port in response to the second input droplet having a radius of curvature less than the radius of curvature of the first output droplet. The first output droplet flows toward the second input port in response the second input droplet having a radius of curvature greater than the radius of curvature of the first output droplet.
The channel network may include a second channel. The second channel has an input port and an output port. The input port of the second channel is positioned in proximity to the output port of the first channel. The first output droplet communicates with the input port of the second channel when the first output droplet exceeds a predetermined volume. A second output droplet may be deposited on the output port of the second channel. The second output droplet has a radius of curvature wherein the first output droplet flows toward the output port of the second channel in response to the first output droplet communicating with the input port of the second channel and having a radius of curvature less than the radius of curvature of the second output droplet on the output port of the second channel.
In accordance with a further aspect of the present invention, a method is provided of controlling communication between multiple ports in a microfluidic device. The method includes the step of providing a channel network in a microfluidic device. The channel network includes a first channel having a first input port and an output port. The first channel is filled with a fluid. A first output droplet is deposited on the output port. The first output droplet has a radius of curvature. A first input droplet is deposited on the first input port. The first input droplet has a radius of curvature. The first output droplet flows toward the first input port when the first input droplet has a radius of curvature greater than the radius of curvature of the first output droplet. The first input droplet flows toward the output port in response to the first input droplet having a radius of curvature less than the radius of curvature of the first output droplet.
The method may include the additional steps of providing a second input port for the first channel and depositing a second input droplet on the second input port. The second input droplet flows toward the output port in response the second input droplet having a radius of curvature less than the radius of curvature of the first output droplet. The first output droplet flows toward the second input port in response the second input droplet having a radius of curvature greater than the radius of curvature of the first output droplet.
The channel network may include a second channel. The second channel has an input port and an output port. The input port of the second channel is positioned in proximity to the output port of the first channel. The first output droplet communicates with the input port of the second channel when the first output droplet exceeds a predetermined volume. A second output droplet is deposited on the output port of the second channel. The second output droplet has a radius of curvature wherein the first output droplet flows toward the output port of the second channel in response to the first output droplet communicating with the input port of the second channel and having a radius of curvature less than the radius of curvature of the second output droplet on the output port of the second channel.